Clutch operating means on motor vehicles



Jan. ll, 1938. K. MAYBACH i CLUTCH OPERATING MEANS ON MOTOR VEHICLES Original Filed Sept. 12, 1935 Patented Jan. 11, 1938.

UNITED 'STATES PATENT OFFICE CLUTCH OPERATING MEANS 0N MOTOR VEHICLES Application September 12, 1933, Serial No. 689,062.

Renewed tember 24, 1932 18 Claims.

My invention relates to clutch operating means on motor vehicles and has special reference to the clutch usually inserted between the motor and the change speed gear.

It has been suggested to provide automatically working clutches for motor cars which at the same time serve for tree-wheeling purposes, and

which in their working are dependent on the.

speed of the motor as well as on' the speed of the vehicle so that they can be operated by the driver simply by giving gas. Generally there are two speed-responsive devices such as centrifugal pendule and, besides, means may be provided for causing automatic declutohing at a certain lowest idling speed which. can be set in accordance to the prevailing circumstances and further providedd with means preventing reclutching until the parts to be coupled rotate at substantially equal speeds, as disclosed in my co-pending applicationserial Number 653,259, filed Jan. 24, 1933. v

According to my invention devices of this kind are further improved and developed in .such manner that the engagement of the clutch takes place gradually dependent on the prevailing resistance oiered to the vehicle and at the same time depending on the way in which the driver gives gas. The movement of the movable clutch member in every phase of the way in which the engagement of the clutch is perfected is automatically adapted to the afore-mentioned two kinds of inuence.

The construction according to the invention is such that as soon as the motor exceeds its pre-determined lowest speed a certain force, for

example the pressure of a controlled pressure means` acts on the member for engaging the clutch: this force increases in dependency on the resistance oered to the vehicle and on the way in which the driver gives gas: and finally when the two clutch members have reached equal speeds of rotation they come to total engagement under the full clutch pressure independent of `thel prevailing absolute speedand independent of the partial clutch pressure prevailing just before.

Furthermore. the arrangement according to my invention works in such manner that automatic declutching is prevented `until the lowest speed of rotation is reached. at this speed the clutch is held disengaged under the highest possible counter-pressure. and as soon as the speed rises the movable clutch member immediately moves over the entire play between the two clutch members. But these members do not yet come August 19, 1936. In Germany Septo final engagement, they simply touch each other, and in the degree in which the motor speed increases the clutch pressure increases also. Upon both clutch members having reached equal speed of rotation the variable clutch pressure which was dependent on the motor speed is suddenly and rapidly replaced by the full and constant clutch pressure, for example that of a spring.

At low starting resistance (good and level road) and when the driver requires only slow acceleration. this arrangement will cause engagement of the clutch even at a very small increase of the number of revolutions of the motor beyond the idle run number of revolutions of the motor. On the other hand with the same low starting resistance, but with a required very high acceleration, the number of revolutions of the motor will increase accordingly (for instance up to 500 -to 1000 revolutions per minute above the idle run c'number of revolutions) before the clutch is final- 1yl engaged. Finally with the highest starting resistance (exceedingly high climb upon a bad road) a still higher number of revolutions is reached which will adjust itself in accordance with the required starting acceleration (for instance one-half or three-quarters of the maximum number of revolutions of the motor).

The employment of the arrangement according to the invention affords particular advantages in connection with such gear controlling devices which on changing do no longer require the clutch to be operated, in which for instance automatic disengaging of the coupling upon stopping the gas supply and if desired also a free run device is provided posterior to the gear, or with'gears the wheels of which are operated bv change clutches without middle idle position of the control'sleeve. In such arrangements, the operating lever of the clutch can be omitted by the employment of an arrangement according to the invention, as the operation of the clutch will then no longer be required even for its ultimate purpose namely the starting under the most difficult conditions.

A further advantage of the arrangement accordine: to the invention consists in that the otherwise extremely diilicult starting upon inclined roads will be substantially facilitated as there will be no need to operate a clutch lever. The driver operates with one foot the brake pedal and with the other foot the gas accelerator. In proportion as the number of revolutions of the motor increases and the clutch is more strongly pressed, thebrake pedal may be released.

The driver can therefore by operating these two levers start the vehicle from standstill even on the steepest inclines, whereas it was hitherto extremely diflicult and often almost impossible owing to the necessity of simultaneously operating the clutch pedal and the accelerator by the two feet and moreover operating the hand brake, to start a vehicle upon an incline without backward running of the vehicle occurring, which is extremely dangerous in mountainous countries. For this reason arrangements have been provided for preventing such a running back. Such special arrangements are with the arrangement according to the present invention likewise no longer necessary.

The invention is applicable to any kind of power driven vehicle, not only cars for the conveyance of persons, omnibuses and power driven vehicles for the conveyance of loads, but also to railroad vehicles with motor drive. With the latter kind of power driven vehicles, the arrangement according to the invention is important inasmuch as with such vehicles the driver often has his position at such distance from the engine plant that he cannot judge and accordingly tune the engaging operation according to the noise of the motor.

A constructional example is shown diagrammatically in the drawing, mostly in section. Subatmospheric pressure is assumed to be the pressure means for actuating the disengaging and en- Basins device of the clutch.

I denotes `a. container from which supply of sub-atmospheric pressure to the device takes place and which may be connected to the intake 1 manifold of the motor. From the container leads a conduit 2 with branches 8 and 4 to the control members. 1 is iluid pump driven from the crank shaft |8-by means of a flexible shaft 8 andworm drive 8. is a second fluid pump .which is driven from the shaft I4 of the clutch part .I5 (car driving shaft) by means of a flexible shaft |2 and worm drive I8. The ily wheel I8 of the motor constitutes at the same time the other clutch half. The clutch is maintained during the run of the car in the engaged position by the spring I1.

In the'casing 5 of the fluid pumps, I8 is a suction space from which the pump driven by the car draws the fluid. I8 is the fluid space located between the two pumps. 8 is a spring loaded suction valve which opens at the greatest permitted sub-atmospheric pressure in the space I8. 28 is the space into which the motor driven pump 1 delivers. 58 is an overpressure valve which prevents a predetermined maximum pressure in the space 28 from being exceeded. In this space there is a slide valve 2| which is loaded by a spring 22 as well as a piston 28, the needleshaped extension 24 of which controls at its lower end the delivery through the opening 25. Above the piston 28 there is a spring 28 and a control slide valve 21, which latter is loaded by a spring 28, the pressure ofthe spring being adapted to be adjusted by the screw 88. 85 is a vent opening. From the space 28 the fluid may also escape through the opening 28 the free cross section of which may be adjusted by the screw 88.

The fluid in the space I8 located between the two pumps can act upon a slide valve-8| which is loaded by a springv82, the two end positions of the slide valve being determined by the stops 88 and 84.

The slide valve 48 is loaded by a spring 42 and is connected by the conduits 8| and 48 with the casing of the slide valve 8|, by the conduits 44 and 48 which are connected to the conduit 4|, to the casing of the slide valve 2|, and by the conduit 48 and its branches 41 and 48 with the casing of the slide valve 21. At the left end of the casing of the slide valve 48 there isa vent opening 88. From the casings oi' the slide valves 48 and 8| conduits 48 and 58 lead to a conduit 8|, the latter opening into the cylinder 52 of the actuating device oi' the clutch. In the actuating device a piston 58 is loaded by a spring 54, and acts by means of a rod 55, a link 58 and a twoarmed lever l1 upon the movable part I5 of the clutch.

'I'he accelerator pedal 8| is connected to the throttle valve 84 by means of rod 82, and return spring 88 is adapted to move pedal 8| back into the position represented after it had been depressed and released again. Clutch pedal 85 is provided with the return spring 88.

l 'I'he mode of operation of the device is as folows:

As long as the vehicle stands still and before the motor is started there isatmospherlc pressure in the motor intake I and also in the conduits 2, 8 and 4. And as pump 1 is not working space 28 contains atmospheric pressure and piston 23 is in its lowest position, as represented. Slide valve 21 by means of springs 28 and 28, acting against each other, is held in a position just a little lower than represented so that space 88 is in connection with conduit 8. 'I'he slide valve 21 possesses both at the top and at the bottom one controlling edge portion each. The upper control edge controls the passage to the conduit 8 which through the conduit 2 leads to the intake manifold I, whilst the lower control edge controls the entry of the outer air into the passage 48.

As there is no pressure in space 28 slide valve 2| is in its lowest position, as represented in the figure, connecting conduit 4 with conduit 4|. Slide valve 48 at its right hand end being under atmospheric pressure through conduits 4| and 45 is in its left hand-position owing to the pressure of spring 42, in which position conduits 46 and 48 are connected with one another, whereas conduit 8| is connected to the atmosphere. Slide valve 8| because of the pressure from spring 32 is in its right hand position in which conduits 5| and 58 are connected to conduit 6| and to the atmosphere by means of channel 68 in slide valve 48. Consequently, there is atmospheric pressure in the space of cylinder 52' which is to the right of piston 53 so that this piston is in its left hand position owing to the pressure of spring 54. In this position of piston 58 clutch members I5 and IB are engaged.

Conduit 46 is in connection with conduit 43, but slide valve 3| being in its right hand position closes this conduit. Conduits 44 and 49 are not connected because slide valve 48 is in its left hand position.

Before starting the driver disconnects the clutch members I5 and I8 by means of the ordinary clutch pedal 85 and then he starts the motor which runs at its lowest idling speed and creates a sub-atmospheric pressure in the intake manifold I. The sub-atmospheric pressure can therefore pass from the container through the conduits 2 and 4, the slide valve 2| and the conduits 4I and 45, behind the right hand side of the slide valve 48, whereby the latter is pulled against the action of the spring 42 into its right hand end position (as illustrated). The conduit 44 which branches oil the conduit 4| is thereby connected with the conduit 48. The full sub-atmospheric pressure acting at the idle run number of revolutions, passes therefore along the path through the conduit 5I, which connects the conduit 49 with the clutch operating cylinder 62, behind the piston 63 of the disengaging device, and the clutch is completely disengaged with the maximum force. v

Before dealing with the further operations occurring during starting, the mode of operation oi' the pressure regulating mem'ber 21 will be rst described. At the fluid pressure corresponding to the idle run number of revolutions, the piston 23 is in its lowest position and the spring 26 is entirely or nearly without tension. 'I'he slide valve 21 possesses both at the top and at the bottom one controlling edge portion each. The upper control edge controls the passage to the conduit 3 which through the conduit 2 leads to the sub-atmospheric pressure container I, whilst the lower control edge controls the entry of outer air into the passage 48. By the action of the two control edges there will be produced in the space 36 above the slide valve 21 and in the adjacent conduits a sub-atmospheric pressure which is lower than that in the container l and depends upon the tension of the spring 28. By altering the tension of the spring 28 by means of the regulating screw 38 the magnitude of the effective sub-atmospheric pressure may be varied. When starting space 36 is connected to the intake manifold I by means of conduits 2 and 3, as explained above, the sub-atmospheric pressure then prevailing in the manifold I causes a sub-atmospheric pressure in space 36 also, and consequently slide valve 21 moves upward into the middle position, as represented in the drawing, so that valve 21 closes both conduits, 48 as well as 3, which means that in this state the weight of valve 21, the pressure of springs 26 and 28 and the sub-atmospheric pressure within space 36 are in equilibrium. Upon increase of the number of revolutions of the motor, therefore upon increase of the uid pressure in the space 20, the piston 23 will be moved upwards and the spring 26 will be more tensioned. The piston 21 will under the increased pressure of the spring 26 perform a small movement upwards. By this movement and through admission of air at the lower control edge of the slide valve 21 into conduits 48, 41, 46 and also into the space 36 above the slide valve 21, the previously existing sub-atmospheric pressure will be slightly reduced in vaccordance with the alteration of the number of revolutions. An increase of pressure will therefore have occurred in the space 36, which will cause the slide valve 21 to move somewhat downwards so as to close again the conduit 48. 'I'he three forces acting upon the slide valve 21: spring 26, the action of the reduced sub-atmospheric pressure, and spring 28 are now again balancing each other. The control movements of the slide valve 21 are, ofcourse, only of a very small size (tenths of a millimetre both upwards and downwards).

During further increase of the number of revolutions and consequent increase of the uid pressure in the space 20, the above-described toand-fro movement is repeated so that a variable sub-atmospheric pressure depending as `regards its magnitude upon the number of revolutions of the motor will automatically be produced in the space 36 and in the conduits communicating therewith.

During starting, only the number of revolutions of the motor is increased by the driver. Even after a small increase of the number of revolutions of the motor above the idle run number of revolutions (for instance an increase of 20 to 3Q revolutions per minute) the slide valve 2I will reach its upper` end position in which the conduit 4 extending from the sub-atmospheric pressure container is closed, and the conduit 4I is connected with the vent opening 62. By this means, air passes through` the conduit 46 behind the right hand end of the slide valve 40, whereby the latter moves under the action o the spring 42 into the left hand end position and closes the passage from the conduit 44 to the conduits 43 and 6I and the clutch operating cylinder 62; At the same time and in this position of the slide valve 40, the passage from the conduit 46 to the conduit 43 is opened.

As the fluid pump II driven by the vehicle is standing still, sub-atmospheric pressure is produced in the space I9 by the fluid pump 1 driven by the motor. Consequently the slide valve II is in its left hand end position (as illustrated). The passage from the conduit 43 to the conduit 50 and consequently also via conduit 5I to the clutch operating cylinder is opened. 'I'he subatmospheric pressure regulated as regards its value by the slide valve 21, will therefore upon the idle run number of revolutions of the motor being slightly exceeded, act with its maximum set value upon the piston 63 of the disengaging device, via conduits 41, 48, slide valve 40. conduit 43. slide valve 3|, conduits Il, 8|, and the previously active full suction sub-atmospheric pressure of the motor will be instantaneously replaced by this maximum value of the reduced sub-atmospheric pressure at the mentioned small increase (of 20 to 30 revolutions per minute) above the idle run number of revolutions. as the slide valve 4 0 suddenly renders free the passage to the conduits 46 and 43 and consequently enablesthe reduced sub-atmospheric pressure to come into action. By this means the piston 63 ofthe disengaging and engaging device and the movable clutch part I5 will instantaneously travel the release stroke from the fully disengaged position to that position in which the clutch parts just contact with each other lightly without proper carrying force. y

According to the number of revolutions of the motor set by the driver by means of the gas lever, the number of revolutions of the pump 1 and consequently the fluid pressure in the space 26 will increase. Consequently the piston 23 will move accordingly upwards and will by compressing the spring 26 act upon the slide valve 21. The effective sub-atmospheric pressure will therefore be altered by the slide valve 21 in dependence of the number of revolutions of the motor, the slide valve 21 being moved forwards and backwards, and the varied sub-atmospheric pressure will act upon the piston 53 of the disengaging device along the described path. The clutch parts will therefore upon the number of revolutions of the motor increasing, be pressed against each other more strongly, in accordance with the decrease of the effective sub-atmospheric pressure, that is the number of revolutions of the motor set by thel driver.

As soon as the number of revolutions is so high that the produced pressure between the parts is sumcient for transmitting the turning moment required for overcoming the starting resistance and for yproducing the desired acceleration, the clutch part I5 will be frictionally/carried. slipping occurring in the clutch, and the vehicle will commence starting.

As soon as subsequently the two clutch parts reach the same number of revolutions, and consequently the two fluid pumps'l and Il run with the same number of revolutions, the sub-atmosphericpressure of the iluid which previously existed in the space I9 between the two pumps will disappear. Consequently the slide valve 3| will, under the pressure of the spring 32, be moved into its right hand position, the passage to the conduit I3 and so on to the space 36 above the slide valve 21 will be closed, and instead the connection of the conduit50 and consequently the cylinder of the disengaging andv engaging device with the outer'air will be established via conduit 6i and the bore B0 of the slide valve I0. Whereas. therefore, before the synchronous run. there was a pressure to engage the clutch which corresponded to the effective sub-atmospheric pressure dependent upon the number of revolutions of the motor at the time being, the clutch is now pressed into engagement with the full force of the spring Il, without any counteracting force of sub-atmospheric pressure, and consequently the clutch will become firmly engaged.4

If during further operation, the number of revolutions of the motor is increased or reduced, this will have no inuence upon the clutch, as the slide valve 3i will remain in its right hand lend position and the clutch engaging cylinder will be permanently connected to air. Only when f the speed of the vehicle is dropped to a speed corresponding to the lowest idle run number of revolutions of the motor, will the slide valve 2| under the action of the spring 22 move into its lower end position owing to the action of the fluid pressure in the space 20 which is dropped to its hicle is stopped, starting may be effected again in the above-described manner. If the vehicle runs on without stopping, the clutch will be maintained in its disengaged position until the number of revolutions of the motor is again increased. Upon the number of revolutions being slightly increased above the idle run number of revolutions of the motor, the slide valve 2i will again move into its upper position and consequently the slide valve 40 will again move into its left end position and the clutch operating cylinder will in the above-described manner finally be connected to air.

Engagement of the clutch takes place always upon synchronous running of the clutch parts and at various numbers of revolutions depending upon starting conditions, without being directly dependent of the position of the gas lever.

Apart from this arrangement which for the sake of clarity has been kept purely diagrammatic and simple, other arrangements may be obviously chosen within the scope of the invention and without changing the essence of the invention.

'I'he slide valve movements and cross sections given in the drawing, are shown in a purely diagrammatic manner. They are in carrying out the invention so chosen as to attain high sensitiveness, and accurate and rapid action of the controlling operations.

I do not want to be limited to the details described or shown in the drawing, as many variations will occur to those skilled in the art.

What I claim is:

1. On a motor driven vehicle in combination: a iii-st clutch member in driving connection with the motor and a second clutch member in driving connection with the wheels of said vehicle; pressure means adapted to cause engagement and disengagement of said clutch members; a first valve for controlling said pressure means in div the motor and a second clutch member in driv-` ing connection with the wheels of said vehicle; pressure means adapted to cause engagement and disengagement of said clutch members; a first valve for controlling said pressure means in direct dependency on the speed of rotation of said motor; a second valve for controlling said pressure means in dependency both on the speed of rotation of said motor and on the speed of rotation of said second clutch member; and means for controlling said pressure means being adapted to cause disengagement of said clutch members when the motor speed is reduced to its idling speed.

3. A combination as claimed in claim 1 further including means for causing the pressure means controlled by said iirst controlling valve to re-act on said rst valve.

4. A combination as claimed in claim 2 further including means for causingr thepressure means controlled by said first controlling valve re-act on said first valve.

5. On a motor driven vehicle in combination: a clutch having a clutch member in driving connection with the motor and a clutch member in driving connection with the wheels of said vehicle; pressure means for engaging and disengaging said two clutch members, said pressure means comprising: a rst uid pressure system adapted to cause regulated pressure to act on said clutch and a second fluid pressure system adapted to cause disengagement and full engagement of said clutch, alternately, said second system having two branches; a rs: valve in said first system for controlling the pressure in dependency on the speed oi rotation of said motor; a second valve in said first system and in one branch of said second system for controlling the pressure in dependency both on the speed of said motor and on the speed of said vehicle and for alternately connecting said first system and one of the branches of said second system to said clutclu' means for controlling said pressure in dependency on the speed of the motor so as to cause disengagement of said clutch when the motor speed is reduced to its idling speed; and means in both said first system and in the two branches of said second system for alternately connecting said first system and one of the branches of said second system to said clutch.

6. On a motor driven vehicle in combination: a clutch having a clutch member in driving connection with the motor and a clutch member in driving connection with the wheels of said vehicle; pressure means for engaging and disengaging said two clutch members; said pressure means comprising: a first fluid pressure system adapted to cause regulated pressure to act on said clutch and a second uid pressure system adapted to cause alternately full pressure and no pressure to act on said clutch andthereby to cause full engagement or disengagement of said clutch, alternately, said second system having two branches; a ilrst valve in said rst system for controlling the pressure in dependency on the speed oi rotation of said motor; `a second valve in said rst and in one branch of said second system for controlling the pressure in dependency both on the speed of said motor and on the speed of said vehicle and foralternately connecting said iirst system or one of the branches of said second system to said clutch; a third valve in said second iluid pressure system con trolling the pressure in dependency on the speed of the motor so as to cause disengagement of said clutch when the motor speed is reduced to its idling speed; and a fourth valve in both said ilrst system and in the two branches of said second system for alternately connecting said iirst system and one of the branches of said second system to said clutch.

'1. A combination as claimed in claim 6 further including the feature that said fourth valve is controlled by said third valve.

8. A combination as claimed in claim 1 further including: a iirst iluid pressure causing device driven by said motor and a second uid pressure causing device driven in dependency on the speed of the wheels of said vehicle; said first device being adapted to act on said iirst valve and both said devices being adapted to act on said second valve.

9. A combination as claimed in claim 2 further including: a first iiuid pressure causing device driven by said motor and a second uid pressure causing device driven in dependency on the speed of the wheels of said vehicle; said first device being adapted to act on said iirst`r valve and both said devices being adapted to act on said second valve. f

10. A combination as claimed in claim 5 further including: a rst fluid pressure causing device driven by said motor and a second fluid pressure causing device driven in dependency on the speed of the wheels of said vehicle; said first device being adapted to act on said first valve and both said devices being adapted to act on said second valve.

l1. On a motor vehicle in combination: a clutch having a clutch member in driving connection with the motor and a clutch member in driving connection with the wheels of said vehicle; pressure means for engaging and disene' gaging said two clutch members, said pressure means comprising: a first fluid pressure system adapted to cause regulated pressure to act on said clutch and a second fluid pressure system adapted to cause the full pressure to act on said clutch, said second system having two branches; a first valve in said rst system for regulating the pressure and being itself under the influence of the regulated pressure; a second valve in said iirst system for controlling. alternatelyv the regulated pressure and the pressure for full engagement of said clutch in dependency both on the speed of said motor and the speed of said vehicle; a third valve in one of said branches of said second fluid pressure system for controlling the full pressure so as to cause disengagement of said clutch when the motor speed is reduced to the idling speed; a .fourth valve in both said systems for alternately connecting one of said systems to said clutch, said fourth valve being controlled by said third valve.

12. A combination as claimed in claim 11 further including: a first liquid pressure pump driven by said motor anda second liquid pressure pump driven in dependency on the speed of the wheels of said vehicle; said iirstpump being adapted to act on said ilrst valve and on said third valve, both said pumps being adapted to act on said second valve.

13. On a motor driven vehicle in combination, a clutch member in driving connection with the motor and a clutch member in driving connection with the wheels of the vehicle, pressure means for engaging and disengaging said clutch members, said pressure means comprising a first fluid pressure system adapted to cause regulated pressure to engage the clutch, valve means in said first system responsive to the speed of the` engine and adapted to regulate the pressure in said first system, a second uid pressure system adapted to cause disengagement of the clutch, and control means for alternately connecting the first system and the second system to the clutch.

14. On a, motor driven vehicle in combination, a clutch member ir driving connection with the motor and a clutch member in driving connection with the wheels of the vehicle, pressure means for engaging and disengaging said clutch members, said pressure means comprising a iirst fluid pressure system adapted to cause regulated pressure to engage the clutch, valve means in said rst system responsive to the speed of the engine and adapted to regulate the pressure in said. first system, a second uid pressure system adapted to cause disengagement of the clutch. and means operating alternately to connect the rst system to the clutch when the motor begins to exceed idling speed and to connect the second system to the clutch when the motor slows down to idling speed.

15. On a motor driven vehicle in combination, a clutch member in driving connection with the motor and a clutch member in driving connection with the wheels of the vehicle, pressure means for engaging and disengaging said clutch members, said pressure means comprising a iirst uid pressure system adapted to cause regulated pressure to engage the clutch, valve means in said iirst system responsive to the speed of the engine and adapted to regulate the pressure in said iirst system, a second iluid pressure system adapted to cause disengagement of the clutch, means adapted to render the second system inoperative to disengage the clutch when the motor exceeds idling speed, and shift means actuatable by said last-mentioned means to alternately connect the iirst system and the second system to the clutch.

16. On a motor driven vehicle, in combination,

a rst clutch member in driving connection with i the motor and a second clutch member in driving connection with the wheels of the vehicle, iluid pressure meansr adapted to cause engagement and disengagement of said clutch members, control means for the pressure means responsive t0 the speed of the motor and selectively operative to cause the pressure means to engage the clutch when the motor exceeds idling speed and to cause the pressure means to disengage the clutch when the motor is at idling speed and pressure regulating means for the pressure means responsive to the speed of the motor and becoming operative when the motor exceeds idling speed to cause regulated pressure to engage the clutch.

17. On a motor driven vehicle, in combination, a first clutch member in driving connection with the motor and a second clutch member in driving connection with the wheels of the vehicle, and clutch actuating pressure vmeans operative to connection with the wheels o! the vehicle, automatic clutch actuating means operating when the motor drops to a predetermined low speed to eiect disengagement of the clutch and operating when the motor exceeds said predetermined iow speed to eect engagement of the clutch, and regulating means for the clutch actuating means operating in dependency both on the speed of the motor above said predetermined low speed and the speed of the second clutch member to cause the clutch actuating means to eiect gradual re-engagement of the clutch.

KARL MAYBACH. 

